Android sdk Firebase

Question

Robię sobie projekt z Firebase i wywala mi teraz taki problem -

Error:Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.dex.DexException: Multiple dex files define Lcom/google/android/gms/internal/zzaso;

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.dex.DexException: Multiple dex files define Lcom/google/android/gms/internal/zzaso;

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

Robię po kolei tak jak jest napisane tutaj https://github.com/firebase/FirebaseUI-Android/blob/master/README.md i tu https://github.com/firebase/FirebaseUI-Android/blob/master/auth/README.md#sign-in-examples . Jak to naprawić?

Jedyną rzeczą jaką zmieniłem to z com.android.support:appcompat-v7:26.+ na 25.3.1 bo wywalało błąd.